Interface Engineering Between multi‐elemental alloy Nanoparticles and Carbon Support Toward Stable Catalysts

In the present study different concepts for the development of bifunctional oxygen reduction reaction / oxygen evolution reaction (ORR / OER) electrocatalysts are explored and compared. Bifunctional ORR / OER catalysts are often suggested to improve the stability during startup and shutdown of fuel cells. Furthermore, they are proposed for so-called unitized regenerative fuel cells (URFCs) that would allow a closed loop system to use and produce hydrogen on demand. We compare the electrocatalytic performance of conventional PtxIry alloy nanoparticles (NPs) with Pt – IrO2 NP composites (nanocomposites), both immobilized onto a commercial carbon support. The Pt – IrO2 nanocomposites thereby consist of a mixture of Pt NPs and IrO2 NPs. By probing the electrocatalytic performance before and after exposing the electrocatalysts to accelerated degradation tests (ADTs) it is shown that the Pt – IrO2 nanocomposite concept offers advantages but also some disadvantages over the conventional alloy concept. In particular it is shown that while the nanocomposites are initially less active for the ORR due to an interparticle effect, their performance is less affected by the ADTs. However, all tested catalysts experience a decline of the Ir / Pt ratio upon the ADTs treatment, highlighting the challenging stability requirements for URFCs.

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Bifunctional Pt-IrO2 Catalysts for the Oxygen Evolution and Oxygen Reduction Reactions: Alloy Nanoparticles vs. Nanocomposite Catalysts

10.26434/chemrxiv.12919190 ◽

2020 ◽

Author(s):

Jia Du ◽

Jonathan Quinson ◽

Daming Zhang ◽

Francesco Bizzotto ◽

Alessandro Zana ◽

...

Keyword(s):

Fuel Cells ◽

Oxygen Reduction ◽

Oxygen Evolution ◽

Carbon Support ◽

Reduction Reaction ◽

Alloy Nanoparticles ◽

Electrocatalytic Performance ◽

Before And After ◽

Nanocomposite Catalysts ◽

The Stability

In the present study different concepts for the development of bifunctional oxygen reduction reaction / oxygen evolution reaction (ORR / OER) electrocatalysts are explored and compared. Bifunctional ORR / OER catalysts are often suggested to improve the stability during startup and shutdown of fuel cells. Furthermore, they are proposed for so-called unitized regenerative fuel cells (URFCs) that would allow a closed loop system to use and produce hydrogen on demand. We compare the electrocatalytic performance of conventional PtxIry alloy nanoparticles (NPs) with Pt – IrO2 NP composites (nanocomposites), both immobilized onto a commercial carbon support. The Pt – IrO2 nanocomposites thereby consist of a mixture of Pt NPs and IrO2 NPs. By probing the electrocatalytic performance before and after exposing the electrocatalysts to accelerated degradation tests (ADTs) it is shown that the Pt – IrO2 nanocomposite concept offers advantages but also some disadvantages over the conventional alloy concept. In particular it is shown that while the nanocomposites are initially less active for the ORR due to an interparticle effect, their performance is less affected by the ADTs. However, all tested catalysts experience a decline of the Ir / Pt ratio upon the ADTs treatment, highlighting the challenging stability requirements for URFCs.

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Bifunctional Pt-IrO2 Catalysts for the Oxygen Evolution and Oxygen Reduction Reactions: Alloy Nanoparticles vs. Nanocomposite Catalysts

10.26434/chemrxiv.12919190.v2 ◽

2020 ◽

Author(s):

Jia Du ◽

Jonathan Quinson ◽

Daming Zhang ◽

Francesco Bizzotto ◽

Alessandro Zana ◽

...

Keyword(s):

Fuel Cells ◽

Oxygen Reduction ◽

Oxygen Evolution ◽

Carbon Support ◽

Reduction Reaction ◽

Alloy Nanoparticles ◽

Electrocatalytic Performance ◽

Before And After ◽

Nanocomposite Catalysts ◽

The Stability

In the present study different concepts for the development of bifunctional oxygen reduction reaction / oxygen evolution reaction (ORR / OER) electrocatalysts are explored and compared. Bifunctional ORR / OER catalysts are often suggested to improve the stability during startup and shutdown of fuel cells. Furthermore, they are proposed for so-called unitized regenerative fuel cells (URFCs) that would allow a closed loop system to use and produce hydrogen on demand. We compare the electrocatalytic performance of conventional PtxIry alloy nanoparticles (NPs) with Pt – IrO2 NP composites (nanocomposites), both immobilized onto a commercial carbon support. The Pt – IrO2 nanocomposites thereby consist of a mixture of Pt NPs and IrO2 NPs. By probing the electrocatalytic performance before and after exposing the electrocatalysts to accelerated degradation tests (ADTs) it is shown that the Pt – IrO2 nanocomposite concept offers advantages but also some disadvantages over the conventional alloy concept. In particular it is shown that while the nanocomposites are initially less active for the ORR due to an interparticle effect, their performance is less affected by the ADTs. However, all tested catalysts experience a decline of the Ir / Pt ratio upon the ADTs treatment, highlighting the challenging stability requirements for URFCs.

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Nonenzymatic sensing of glucose at neutral pH values and low working potential using a glassy carbon electrode modified with platinum-iron alloy nanoparticles on a carbon support

Microchimica Acta ◽

10.1007/s00604-015-1580-y ◽

2015 ◽

Vol 182 (15-16) ◽

pp. 2395-2401 ◽

Cited By ~ 8

Author(s):

He Mei ◽

Qu Sheng ◽

Huimin Wu ◽

Xiuhua Zhang ◽

Shengfu Wang ◽

...

Keyword(s):

Glassy Carbon Electrode ◽

Glassy Carbon ◽

Iron Alloy ◽

Carbon Support ◽

Alloy Nanoparticles ◽

Carbon Electrode ◽

Nonenzymatic Sensing ◽

Ph Values ◽

Neutral Ph

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Structural similarity of ribosomes from E. coli and A. salina

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100082078 ◽

1978 ◽

Vol 36 (2) ◽

pp. 242-243

Author(s):

M. Boublik ◽

R.M. Wydro ◽

W. Hellmann ◽

F. Jenkins

Keyword(s):

Ribosomal Proteins ◽

Direct Evidence ◽

Structural Similarity ◽

Carbon Support ◽

Artemia Salina ◽

Uranyl Acetate ◽

Biological Assays ◽

E Coli ◽

And Function ◽

Fine Carbon

Ribosomes are ribonucleoprotein particles necessary for processing the genetic information of mRNA into proteins. Analogy in composition and function of ribosomes from diverse species, established by biochemical and biological assays, implies their structural similarity. Direct evidence obtained by electron microscopy seems to be of increasing relevance in understanding the structure of ribosomes and the mechanism of their role in protein synthesis.The extent of the structural homology between prokaryotic and eukaryotic ribosomes has been studied on ribosomes of Escherichia coli (E.c.) and Artemia salina (A.s.). Despite the established differences in size and in the amount and proportion of ribosomal proteins and RNAs both types of ribosomes show an overall similarity. The monosomes (stained with 0.5% aqueous uranyl acetate and deposited on a fine carbon support) appear in the electron micrographs as round particles with a diameter of approximately 225Å for the 70S E.c. (Fig. 1) and 260Å for the 80S A.s. monosome (Fig. 2).

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Radiation Damage of Support Films

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100096862 ◽

1981 ◽

Vol 39 ◽

pp. 28-29

Author(s):

H.A. Cohen ◽

W. Chiu

Keyword(s):

Transfer Function ◽

Low Temperatures ◽

Carbon Support ◽

Contrast Transfer Function ◽

Electron Dose ◽

Imaging Parameters ◽

Negative Stain ◽

Phase Corrections ◽

Two Parameters ◽

Medium Dose

The goal of imaging the finest detail possible in biological specimens leads to contradictory requirements for the choice of an electron dose. The dose should be as low as possible to minimize object damage, yet as high as possible to optimize image statistics. For specimens that are protected by low temperatures or for which the low resolution associated with negative stain is acceptable, the first condition may be partially relaxed, allowing the use of (for example) 6 to 10 e/Å2. However, this medium dose is marginal for obtaining the contrast transfer function (CTF) of the microscope, which is necessary to allow phase corrections to the image. We have explored two parameters that affect the CTF under medium dose conditions.Figure 1 displays the CTF for carbon (C, row 1) and triafol plus carbon (T+C, row 2). For any column, the images to which the CTF correspond were from a carbon covered hole (C) and the adjacent triafol plus carbon support film (T+C), both recorded on the same micrograph; therefore the imaging parameters of defocus, illumination angle, and electron statistics were identical.

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Experiments in Bright-Field Imaging with Hollow-Cone Illumination

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100097703 ◽

1981 ◽

Vol 39 ◽

pp. 226-227

Author(s):

W. Kunath ◽

K. Weiss ◽

E. Zeitler

Keyword(s):

Signal To Noise Ratio ◽

Carbon Support ◽

Electronic System ◽

Optic Axis ◽

Hollow Cone ◽

Signal To Noise ◽

Bright Field ◽

Noise Ratio ◽

Single Field ◽

Field Imaging

Bright-field images taken with axial illumination show spurious high contrast patterns which obscure details smaller than 15 ° Hollow-cone illumination (HCI), however, reduces this disturbing granulation by statistical superposition and thus improves the signal-to-noise ratio. In this presentation we report on experiments aimed at selecting the proper amount of tilt and defocus for improvement of the signal-to-noise ratio by means of direct observation of the electron images on a TV monitor.Hollow-cone illumination is implemented in our microscope (single field condenser objective, Cs = .5 mm) by an electronic system which rotates the tilted beam about the optic axis. At low rates of revolution (one turn per second or so) a circular motion of the usual granulation in the image of a carbon support film can be observed on the TV monitor. The size of the granular structures and the radius of their orbits depend on both the conical tilt and defocus.

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